Hi,
Whenever you have a non-working board like this, the key thing is to break the problem into manageable chunks. If you do some basic tests, it will help you isolate where the problem is.

1) Verify that all the ICs are receiving proper power and ground. Are any of the chips feeling too hot etc?
2) Verify that all of the external connections (like control voltages and triggers) are actually reaching their destinations properly. For instance, when you turn the knobs for the VC controls, can you see the voltages changing properly on the board?
3) If all of that is correct, then you have to start debugging it step by step. When you inject a trigger pulse to the input of the card, can you follow that signal along through the various components like the NOR gate and so on?

It's really important to gather as much data as you can before you ask for help. Quite often just going through that process can help you find the problem. If not, then it gives us enough information to be able to help you more effectively...

1. All pots are between 0v-15v.
2. Power rail has 6.2V, probably due to working with +-15V.
3. Traced trigger signal all the way to 4016. PINs 9&3 are static at 2.1V.
4. PINs 2&10 show trigger signal and amplitude is impacted by the sustain pot.

Saw that U1 Pin 1 shows 15V, so I removed the TL074 and the module started to behave better. Attack, Sustain, Delay and Release pots worked, while Decay did not.

As TL074 is also in charge of the 5V rail, its removal also reduced that rail to 3.2V, but the module did work as mentioned above._________________Erez Yaary

Ok - lets fix that first -
According to my calculations, if you change R20 to 68k, that should put you right at 5V. That's probably not a big deal, but it definitely affects a lot of different things on the card.

The 15V on pin 1 of U1 does seem strange - I don't have one of these modules so I can't tell what to expect there. Perhaps someone else here can jump in and give us some data...

Which transistors need to be matched? I don't know how to read a schematic so I can't tell what part T1 T2 T3 and T4 refer to.

I suggest you learn to read a schematic before attempting to build this module. Ken makes it very clear on his site that these are not beginners projects and a Serge VC-ADSR is up there in the quite difficult category.

U3 pin 1 is connected to a 22k resistor, the other end of this resistor is connected to the emitters on T1-4. Just follow the track to the 4 transistors.....or it is the 4 trannies in a row next to the LM324

There's very few VC-ADSRs solutions for someone on a budget... I do stick to projects with parts kits and where I don't have to look at the schematic whenever possible.

All I really need is a few questions answered here or there, so thanks for answering my question. I am looking at the schematic and now I see T1 T2 T3 T4. I see it's next to U3. Now, how do I know that U3 is LM324?

It doesn't. you have to read the schematic carefully in conjunction with the text description and the bill of materials at the end. There are 9 transistors T1- T4, an unlabelled (T5), T6,7, and 8, and (T9) unlabelled and greyed out. T1, T2 and T8 are PNP transistors (note the arrow pointing inwards rather than outwards on the symbol), and the parts list gives 3 PNPs, which can be PN4250 or BC557. T6, T7 and the grey one (T9) are noted as PN3565 - and four of those are listed in the BoM. T3 and T4 are NPNs, and (to me) it makes sense that those are the two 2N5089/BC547 listed, since BC547s are the counterpart to BC557s, and T1-T4 are clearly all part of the same subcircuit. So T5 must be the fourth PN3565.

As andrewF said, this is NOT an easy build, and the schematics are not fully explained. Note I haven't built this myself, so the above is just my reading of Ken's webpages.

Arg: working out how the pcb traces match the schematic isnt hard, it just takes some work. it gets easier after you've done it a few times -- being handed the answer might be a short-term solution to this problem, but it would rob you of the opportunity to gain the skill for the next time.

otoh, this is the reason why many PCB designers put th component designators (T1, T2, T3 etc) on the board rather than the values... makes it explicit how the board and schematic match. it's a tradeoff, tho: having the values on the board makes it easier to stuff, having the designators makes it easier to troubleshoot. i prefer ken's approach, and it's what i do on the boards i design. very occasionally i've seen folks do both, but that becomes very cluttered....

But my mindset is always "I'm going to learn this so someone else doesn't have to, so someone else doesn't have to waste their money, waste their time with millions of mistakes, etc." Actually, that really explains my entire life. And it's the same with SDIY.

You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot vote in polls in this forumYou cannot attach files in this forumYou can download files in this forum

Please support our site. If you click through and buy from our affiliate partners, we earn a small commission.